Tow treatment for preparation of high-bulk yarns



May 20, 1969 E. POLACCO ETAL 3,444,682

TOW TREATMENT FOR PREPARATION OF HIGHBULK YARNS V I Filed Aug. 9. 1966 CBULKED 0 NOT BULKED Hw98765 32 x .hIQZWJ kqwkm 2O 3O 4O 96 ELONGATIONEZIO 2332%? F/ G. 4. FRANCESCO 05m":

M? ATTORNEY$ United States Patent Int. (:1. 1m 3/02; D01d 5/20 US. Cl,57140 Claims ABSTRACT OF THE DISCLOSURE wholly oriented staple fiber ofa polymer of acrylon1tr1le comprised of sharply defined alternatesegments B and A along its longitudinal axis, said segment B being ofreduced denier with respect to segment A by reason of its having beenstretched to a length of about 1.1 to 2 times as great as that of thesaid segment A. Also, staple fibers of the aforesaid type after havingbeen shrunk 1n tensionless condition and yarns and fabrics comprised ofsuch staple, Further, processes for the preparation of such staplepredicated upon heat plasticizing a tow of oriented and relaxedfilaments in repeating spaced segments, then stretching said tow,cutting the same into staple and, where appropriate, shrinking the same.

This invention relates to a process for the treatment of two for thepreparation of novel high-bulk acrylic yarns.

More particularly, this invention relates to the prepmatron of high-bulkyarns comprising acrylonitrile polymers which possess uniform dyeingcharacteristics and texture.

High bulk acrylic yarns are known in the art to provide fabrics havingenhanced apparent value and cover. They are commonly provided byblending fibers having different physical characteristics such asshrinking and filament configuration, whether mechanically orself-induced. In the latter case bifilar or bicomponent fibers whereinthe two components shrink differently to thereby cause crimp formationcan be blended with monocomponent fibers to provide yarns from whichfabrics, including carpets, having excellent cover and apparent valuecan be manufactured. While this technique is widely employed andprovides excellent products, economics and processing difiicultiesdemand other methods for producing high bulk yarns.

Thus, an alternate means for preparation of high bulk yarns lies in theblending of fibers which are different at least to the extent that theypossess considerable variation in their ability to shrink upon treatmentwith heat. One known technique to achieve this type of blend lies infeeding separate tows having differing heat shrinkage properties to astaple cutter to thereby achieve a staple fiber blend in the desiredproportion. One salient difliculty with such a blend lies in theobservation that in subsequent textile processing operations, such ascarding, combing and the like, the high shrinking fibers tend to migratetoward the core of the yarn thereby to create a yarn characterized, moreor less, by a high shrinking core and even though such yarns developbulk when subjected to heat treatment, they suffer losses of strengthand aesthetic value,

More recently, attempts have been made to overcome the tendency forfibers to migrate in high bulk yarns as above indicated by the provisionof yarns made from tow having continuously varying shrinkage propertiesalong the longitudinal axis. Such a tow may have, for

example, from zero up to about 20 percent difference in shrinkage whichvaries along the length of the tow so that if the percent of shrinkageupon heat treatment were plotted against the length of the tow the plotwould be sinusoidal. In practice, however, achievement of shrinkagedifferential large enough to provide good bulk characteristics in a yarnrequires such a Wide oscillation period that staple fibers prepared fromsuch tows vary so greatly that the yarn tends to resemble a high-lowshrinkage blend as above discussed.

It therefore becomes an object of the invention to provide a novel bulkyacrylic yarn having uniformity, strength and high bulk.

Another object of the invention lies in the provision of a novel processfor treatment of tow comprising filaments of acrylonitrile polymers toprovide high-bulk yarns.

Additionally, this invention has as its object a novel staple fibercomponent of high-bulk yarns.

These and other objects of this invention are achieved by stretching apreviously oriented and relaxed continuous tow comprised of filaments ofacrylonitrile polymers having regularly intermittant heat plasticizedsegments along its length to provide a wholly oriented filamentary towhaving repeating spaced segments of less than staple fiber length alongthe length of the tow which have been stretched to a greater degree thanthe remaining segments.

The tow having repeating spaced segments of fiber which have beenstretched to a greater degree than the remaining segments may beprepared by continuously passing the tow over a heated roll having achanneled or tooth-like surface so that when the tow is passed over theroll only certain segments of the tow come into contact with the heatedsurface to thereby become plasticized. The tow having spaced plasticizedsegments is passed from the channeled roll in the plasticized conditionto a set of draw rolls moving at a greater peripheral speed than thechanneled roll thereby causing the partially plasticized tow to stretchin those segments which are in a heat plasticized state.

The tow obtained according to the process of this invention ischaracterized in that it is composed of individual filaments havingregularly alternating stretched segments B which segments are heatshrinkable and segments A which receive no stretch according to theinstant invention and which are not heat shrinkable or heat shrinkableonly to a minor degree. The tow can then be cut to staple fiber of adesired length wherein each fiber component has high and low shrinkagesegments along its longitudinal axis. Heat shrinkage of yarns preparedfrom these staple fibers creates a novel yarn which possesses uniformdyeing characteristics, high strength and high bulk.

The lengths of the high shrinking and low shrinking segments built intothe tow (and the resulting ratio of B/A) must be chosen withconsideration of characteristics desired in the final yarn such as bulk,fiber length, degree of heat shrinkage and the like. Preferably, thelength of the high shrinking segments should be between about 15 andmillimeters. Similarly, the length of low shrinking segments should liebetween about 15 and 100 millimeters. The choice of the lengths of thedifferent segments should be such that the sum of A and B equals the cutlength of the staple desired for conventional textile processinggenerally between about 80 and millimeters.

The invention may be more clearly understood by reference to theaccompanying drawing wherein;

FIGURE 1 represents a schematic of yarn treatment according to theinstant process,

FIGURE 2 represents an illustration of a length of filament treatedaccording to the instant process,

FIGURE 3 represents the length of filament shown in FIGURE 2 treatedaccording to this process and having been subsequently heat shrunk and,

FIGURE 4 is a graph showing the stress-strain curves of yarn preparedaccording to this invention and an unbulked yarn.

More particularly, FIGURE 1 illustrates the .process of this inventionwherein a tow 1 of a previously uniformly stretched and relaxedacrylonitrile polymer fiber is continuously passed .to feed rolls 2 and3 and then to an idler roll 4 from whence the tow is passed on to theheated surface of channeled roll 5 which rotates (clockwise direction inFIGURE 1) at the same peripheral speed as feed rolls 2 and 3. Portionsof the tow 1 contact heated roll 5 at heated teeth or contact elementsrepresented by tooth or element 9 which may be an integral or permanentpart of roll 5 or it may be attached as by screw, bolt or other means10. Thus, segment A of tow 1 does not contact the surface of roll 5,while segment B of tow 1 contacts the heated surface of the roll asillustrated and is heated to the extent that it is plasticized. Uponleaving roll 5 tow 1 possessing continuously repeating A and B segmentsalong its length is fed over idler roll 6 to draw rolls 7 and 8 whichrolls rotate at a higher peripheral speed than rolls 2, 3, and 5 therebycausing the tow 1 to be stretched to a length of from about 1.1 to 2times the length fed to rolls 2 and 3. Insofar as the repeating segmentsB leave roll 5 in a plasticized condition, all of the stretch applied tothe tow occurs in these segments whereas segments A remain unmodified.As above indicated, channeled roll 5 presents a toothed surface to thetow wherein heat transfer is effected to the tow passing in contact withthe heated surface of the teeth on roll 5. The several teeth may presentuniform or difierent peripheral lengths of contact to the tow beingpassed over roll 5. Similarly, the peripheral lengths of the spacingsbetween the several teeth may vary or be uniform. Moreover, theirperipheral lengths may be the same as or differ from the peripherallengths of the teeth. By suitably varying the profile of the channeledor toothed roll and the number of teeth or raised contact elements, itis possible to obtain a wide variety of combinations of stretch, stretchratios, ratios between stretched and unstretched segments, and the like.Preferably, the outer surface of the raised contact elements have arectangular shape although this is not a critical aspect of theinvention so long as there is suflicient contact surface to transferheat to the tow.

Roll 5 may be heated by electrical means, by high pressure steam, or byother suitable means for elevating the temperature of the teeth orraised contact elements to cause suitable softening or plasticizing ofthe filamentary material passing in contact therewith. The temperaturesnecessary to plasticize the filaments or tow lie between about 60 andabout 200 C., more typically between about 90 and about 180 C.

Upon leaving draw rolls 7 and 8 the individual filaments of tow 1 may becharacterized by segments along their lengths having sharply varyingdenier caused by differential stretching as depicted in FIGURE 2. Thus,A in FIGURE 2 represents that portion of the filament which isessentially unmodified by passing over roll 5 whereas adjacent segment Bhas been heat plasticized and stretched to thereby cause some reductionin denier at sharply defined points along the length of the filament.Upon subjecting the filament depicted in FIGURE 2 to heat shrinkage thedifferences in denier disappear for all practical purposes and thefilament represents a substantially uniform denier as depicted in FIGURE3 having essentially uniform segment AB"A.

As above indicated this invention is applicable to yarns comprised offilaments of acrylonitrile polymers. These include polyacrylonitrile andinterpolymers comprising at least about weight percent of acrylonitrileand up to about 15 percent of one or more monoethylenically unsaturatedmonomers interpolymerizable therewith. Comonomers such as methylmethacrylate, vinyl acetate, styrene, vinylidene chloride, vinylbromide, vinylpyridine, alkenyl and alkenyloxysulfonic acids, and thelike may be interpolymerized in minor amounts with acrylonitrileaccording to means well known in the art to form useful fiber formingpolymers. The polymers of acrylonitrile, useful for this invention, maythen be dissolved to form spinning solutions in dimethylsulfoxide,dimethylformamide, dimethylacetamide or the like and thereafter extrudedby wet, dry, or dry jet-wet methods to form a multi-filament bundle ofsynthetic filaments which is coagulated, washed, stretched, dried andrelaxed by any of several well known prior art processes. The towtreated according to this invention may be given a mechanical crimpafter treatment on roll 5 to facilitate handling in subsequent textileoperations such as combing and carding.

Moreover, roll 5 may be used to replace the heating plates in machinessuch as the Turbo-Stapler, the Seydel or Termatex converters and othermachines employed to convert tow into top. The top thus obtained iscomprised of individual fibers each having high and low shrinkingsegments along their longitudinal axes.

The following examples are given to illustrate the invention and shouldnot be construed as defining the limits thereof insofar as variationsincorporating the spirit of the invention hereinafter defined by theclaims will be readily apparent to those skilled in the art. The bulkvalues reported were obtained using a Yarn Bulkometer by Linra.

Example I A 40,000 filament tow of a polymer of 94 weight percentacrylonitrile and 6 weight percent vinyl acetate having a total denierof 120,000 having been stretched and relaxed was fed to a pair of feedrolls corresponding to roll 2 and 3 in FIGURE 1 and thereafter passedover a channeled roll corresponding to roll 5 heated to 130 C. and on todraw rolls 7 and 8. The peripheral speed of rolls 2 and 3 was 23 metersper minute while rolls 7 and 8 were run at a peripheral speed of 27.5meters per minute to give the tow a 1.2x stretch. The hot channeled rollhad an outer diameter of 300 millimeters with uniform raised contactsurfaces of 30 millimeter spaced surfaces and channels spacing theraised contact surfaces of 55 millimeters, the ratio of heated contactperiphery to spaces being 30/ 55 The tow thus treated was thereafterpassed to staple cutter and cut to a length of millimeters to provideindividual staple fibers having both stretched and unstretched segments.

The staple fiber was then processed according to the worsted system toprovide a yarn having the following properties:

Metric count(nm.) 34/2 Twist 340 Z+220 S Bulk 6-7 The yarn was thenarranged in hanks, treated with boiling water in a dyeing cabinet andthereafter centrifuged and dried. The boiling water treatment caused theyarn to bulk uniformly to provide the following modified properties:

Metric count(nm.) 27/2 Twist 420 Z+275 S Bulk 18 fabric so obtained wascompared with a knitted fabric of the same compactness the fibers ofwhich had not been treated according to the process of this invention.The novel fabric exhibited better stitch clarity and pilling (afterhours of Random Tumbler) of 12 mg./dm. as compared with 14 mg./drn. forthe control fabric. Handle of the two fabrics was essentiallyequivalent.

Example II The procedure of Example I was repeated using a 100,000denier tow comprised of 20,000 filaments under the following condition:

Stretch 1.15 Length of B segment millimeters Length of A segment do 60Ratio B/A 25/60 Channeled roll temp. C 100 Staple length millimeters 100The yarn obtained by the worsted processing cycle shows the followingcharacteristics:

Metric count (nm.) 54/2 Twist 340 Z+220 S Bulk 6-7 After heat treatmentwith steam the yarn characteristics were:

Metric count 27/2 Twist 420 Z+275 S Bulk 19 Example 111 RepeatingExample I with a 480,000 denier tow comprised of 60,000 filaments anovel yarn was prepared under the following conditions:

Stretch 1.5 X Length of B segment ..millimeters 45 Length of A segmentdo Ratio of B/A /40 Channeled roll temp. C 180 Length of staplemillirneters 100 The yarn obtained was worked up according to theworsted wool cycle and showed the following characteristics before andafter heat treatment by steam:

Before After Metric count (nm.) 34/2 26/2 Twist 320 Z+220 S 420 Z+275 SBulk 6-7 17 Elongation and recovery characteristics of the bulked yarnwere similar to those of woolen yarns of corresponding bulkiness.

Example IV A 480,000 denier tow comprised of 160,000 acrylonitrile/vinylacetate (94/6) filaments was processed on a TurboStapler in which theheating plates had been replaced by a channel roll under the followingconditions:

Feeding speed meters/rninute 23 Stretch 1.15 Roll temp. C 16 0 Stretchat break ratio 3:20 Nominal cut inches 6 The channeled roll used inplace of the heating plates had a diameter of 300 millimeters, thecontact lengths being 25 millimeters and the spaces being millimeters.

Metric count (nm.) 23/2 Twist 390 Z+250 S Bulk 17 In comparison withbulked yarn obtained by conventional methods on a Turbo-Stapler, theyarn prepared as above described shows superior mechanical strength andexhibited a more uniform bulkiness. A plain knitted fabric having astitch length of 5 .6 millimeters and compactness of 10 was manufacturedusing the top above obtained and compared with a fabric manufacturedfrom conventional top having the same compactness. The fabric of thisinvention showed superior stitch clarity and pilling of 4. 8 as comparedwith 6.5 mg./dm. Handle was definitely softer than the control.

FIGURE 4 shows stress-strain curves wherein C represents yarn preparedaccording to this example and D represents yarn prepared fromconventional Turbo-tip. The break length is the length of yarn inkilometers required to break the yarn under its own weight. The curveplotted for the yarn prepared from tow treated according to the instantinvention exhibits a more uniform development.

We claim:

1. Staple fibers, cut from a tow of wholly oriented filaments of apolymer of acrylonitrile having sharply defined alternate segments B ofreduced denier along its longitudinal axis and said segments B being ofless than staple fiber length and having been stretched to lengths about1.1 to 2 times greater than the lengths of the remaining segments A ofthe tow, said remaining segments A also being of less than staplelength, with the lengths of the respective segments being such that thesum of A and B equals the cut length of the staple.

2. A wholly oriented staple fiber of a polymer of acrylonitrilecomprised of sharply defined alternate segments B and A along itslongitudinal axis, said segment B being of reduced denier with respectto segment A by reason of its having been stretched to a length about1.1 to 2 times as great as that of the said segment A.

3. Staple fibers according to claim 2 exhibiting substantiallyhomogeneous cross-sections along their longitudinal axes by reason oftheir additionally having been shrunk in tensionless condition, wherebythere were effected substantially uniform deniers thereof.

4. High-strength, high-bulk yarn susceptible to more uniform dyeing,comprised of the staple fibers of claim 3.

5. A fabric of the yarn of claim 4.

6. Yarn comprised of staple fibers according to claim 2.

7. A process for the preparation of wholly oriented staple fibers of apolymer of acrylonitrile individually comprised of sharply definedalternate segments B and A along their longitudinal axes, said segmentsB being of reduced diameter with respect to segments A by reason oftheir having been stretched to lengths about 1.1 to 2 times as great asthat of the said segments A, comprising heat plasticizing a tow oforiented and relaxed filaments of a polymer of acrylonitrile inrepeating spaced segments along the longitudinal axis of the tow,thereafter stretching said tow about 1.1 to 2 times while the heatplasticized repeating spaced segments thereof are still in a plasticizedcondition, and thence cutting the said tow into staple lengths of frombetween about and millimeters.

8. The process as defined by claim 7, further comprising shrinking saidwholly oriented staple fibers in tensionless condition, whereby thereare obtained staple fibers exhibiting substantially homogeneouscross-sections along their longitudinal axes.

9. The process as defined by claim 7, wherein the tow is heatplasticizedin repeating spaced segments along its longitudinal axis bypassing said tow in longitudinal con tact with repeating spaced heatingelements situated on the periphery of a roll.

10. A process for the preparation of high-strength, high-bulk yarnsusceptible to more uniform dyeing, comprising heat plasticizing a towof oriented and relaxed filaments of a polymer of acrylonitrile inrepeating spaced segments along the longitudinal axis of the tow,thereafter stretching said tow about 1.1 to 2 times while the heatplasticized repeating spaced segments thereof are still in a plasticizedcondition, and then cutting the said tow into staple length of frombetween 8 0 to 120 millimeters to form staple fibers, forming a yarnstructure of said wholly oriented staple fibers and thence shrinking the8 References Cited UNITED STATES PATENTS 2,296,394 9/ 1942 Meloon.

5 2,917,779 12/1959 Kurzke et a1.

2,952,116 9/1960 Burleson 5734 XR 2,975,474 3/1961 Smith. 3,017,684 1/1962 Pittman 2872 3,116,197 12/1963 Kasey.

STANLEY N. GILREATH, Primary Examiner.

W. H. SCHROEDER, Assistant Examiner.

US. Cl. X.R.

same in tensionless condition whereby there are effected 15substantially uniform deniers thereof.

